1. Field of the Invention
The present invention relates to a method for evaluating a lithography system for producing devices such as semiconductor elements, liquid crystal display elements, plasma display elements, and thin film magnetic heads. In particular, the present invention is preferably applied to a lithography system provided with a resist coater, an exposure apparatus, and a developing apparatus (developer).
2. Description of the Related Art
In order to respond to the improvement in degree of integration and degree of fineness of the semiconductor device, it is demanded to enhance the image formation characteristics such as the resolving power and the transfer faithfulness for the exposure apparatus to be used for the lithography step (representatively comprising the application step, the exposure step, and the resist development step) in order to produce the semiconductor device. In order to enhance the image formation characteristics as described above, for example, the following means are adopted for the exposure apparatus. That is, the wavelength of the exposure light beam as the exposure beam is shortened, the numerical aperture of the projection optical system is increased, and the new illumination system such as the modified illumination is developed.
In order to evaluate how the image formation characteristic is actually improved when the exposure condition (for example, the exposure wavelength, the numerical aperture of the projection optical system, and the illumination system) is changed, for example, the following procedure has been hitherto adopted. That is, an image of a line-and-space pattern having a line width approximate to the resolution limit is projected onto a wafer applied with photoresist by the aid of a projection optical system. For example, the line width of the resist pattern, which is obtained after development of the wafer, is measured with the scanning electron microscopy (SEM). An obtained result of the measurement is compared with the data having been measured and stored. However, in the case of this method, the following inconvenience arises. That is, the equipment for performing the evaluation is expensive, because the scanning electron microscope is required in addition to the exposure apparatus. Further, the operation to perform the evaluation is complicated, and the period of time required for the evaluation is prolonged.
In view of the above, in order to conveniently evaluate the image formation characteristic of the exposure apparatus, the following evaluation method has been suggested, as disclosed in Japanese Patent No. 2530080. That is, a plurality of resistor patterns are formed on a semiconductor substrate by using an exposure apparatus and an etching apparatus. The size of the resistor pattern is indirectly determined by measuring resistance values of the resistor patterns.
As described above, the method for performing the evaluation relatively conveniently has been hitherto suggested for the image formation characteristic of the exposure apparatus alone. However, the final shape of the circuit pattern of the semiconductor device is affected not only by the image formation characteristic of the exposure apparatus but also, for example, by the uneven application caused when the photoresist is applied onto the wafer with a resist coater and the uneven development caused when the wafer (photoresist) is developed with a developing apparatus. Therefore, it is not easy to evaluate the image formation characteristic of the exposure apparatus alone after the exposure apparatus is once incorporated into the device-producing line including, for example, the resist coater, the developing apparatus, the baking apparatus, and the cooling apparatus.
On the other hand, in order to respond to further advance of integration of the semiconductor device, it is necessary to improve the accuracy of device production as brought about by the entire lithography system by optimizing the performance of the individual apparatuses including, for example, the exposure apparatus, the resist coater, and the developing apparatus which are included in the lithography system.
The present invention has been achieved from the viewpoint as described above, a first object of which is to provide an evaluating method for effectively evaluating the performance of individual apparatuses incorporated into a lithography system. A second object of the present invention is to provide a method for evaluating and/or adjusting a lithography system in order to improve the device-producing accuracy of a lithography system. A third object of the present invention is to provide a lithography system which makes it possible to effectively evaluate the performance of individual apparatuses incorporated into the lithography system.
Further, a fourth object of the present invention is to provide an adjusting method which makes it possible to easily adjust characteristics of a substrate-processing apparatus for constructing a lithography system together with an exposure apparatus. Still another object of the present invention is to provide an exposure apparatus which makes it possible to carry out the evaluating method as described above.